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    <title>Document</title>
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    <ul>
        <li>富士山下</li>
        <li id="eason">富士山下</li>
        <li>富士山下</li>
        <li>富士山下</li>
    </ul>

    <script>
        let eason=document.querySelector('#eason')
        // 获取兄弟节点  
        console.log(eason.nextSibling);  
        console.log(eason.previousSibling);


        //  获取兄弟元素节点
        console.log(eason.nextElementSibling);   // nextElementSibling  下一个元素的兄弟节点 
        console.log(eason.previousElementSibling);  //  previousElementSibling   上一个元素的兄弟节点 
    </script>
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